Section 54(3)(b) in Tamil Nadu Combined Development and Building Rules, 2019
(b)Septic Tanks. - (i) Where a septic tank is used for sewage disposal, the location, design and construction of the septic tank shall conform to requirements of the National Building Code and as per provisions in G.O.Ms. No 106, MAWS Dept., dated 01.09.2014 (operative guidelines for sept age management for local bodies)(ii)Location of the Septic Tanks and Subsurface Absorption System: A subsoil dispersion system should preferably not be closer than 18m from any source of drinking water, such as well, to mitigate the possibility of bacterial pollution of water supply.(iii)Requirements.-